Two trains 'A' and B' of length 'l' and ‘4l' are travelling into a tunnel of length 'L' in parallel

Two trains 'A' and B' of length 'l' and ‘4l' are travelling into a tunnel of length 'L' in parallel tracks from opposite directions with velocities 108 km/h and 72 km/h, respectively. If train 'A' takes 35 s less time than train 'B' to cross the tunnel then, length 'L' of tunnel is:(Given L = 60l)[April 13, 2023 (I)] (a) 1200 m (b) 2700 m (c) 1800 m (d) 900 m